#include <vector>
#include <set>
#include <stdlib.h>

using namespace std;

#include <iostream>

int main( int argc, char * argv[] ) {

    int runs = 0;
    cin >> runs;

    vector< int > deck;
    for ( int i = 0; i < 13; i++ ){
	for ( int j  = 0; j < 4; j++ ) {
	    deck.push_back( i );
	}
    }

    int total = 0;
    int won = 0;

    for ( int i = 0; i < runs; i++ ) {
	set< int > choose;
	set< int > hand;

	while ( choose.size() < 6 ) {
	    unsigned n = choose.size();
	    int r = rand() % 52;
	    choose.insert( r );
	    if ( choose.size() > n ) {
		hand.insert( deck[ r ] );
	    }
	}

	total++;

	if ( hand.size() < 6 ) {
	    won++;
	}
    }
    
    cout << (double)won / (double)total << endl;
}
